As an apparatus for non-invasively measuring internal information of a living object, such as a head or breast, an apparatus that makes use of light absorbing characteristics of the living object to acquire the internal information has been proposed (refer, for example, to Patent Document 1). With such a measuring apparatus, light is irradiated from
a predetermined irradiation position to a region of a living object to be measured, light that is propagated while being scattered in an interior of the measured region is detected at a predetermined detection position, and from a measurement result of an intensity, time waveform, etc., of the detected light, internal information on the measured region, that is, information on a light absorbing body, such as a tumor, etc., present in the interior of the measured region can be acquired.
Also in Patent Document 1, it is described that a medium (hereinafter, referred to as an “optical interface material”), having substantially the same optical characteristics as the measured region at a wavelength of the irradiated light (measurement wavelength), is interposed between the measured region and the light irradiation position and between the measured region and the detection position to prevent reflection, scattering, etc., of light at a surface of the measured region and thereby improve measurement precision.    Patent Document 1: Japanese Published Examined Patent Appliction No. 3771364